1. Field of the Invention
This inventions relates to the field of hydraulically actuated cutting and punching, and more particularly to an apparatus for punching holes and slots in tubes or channels.
2. State of the Prior Art
Shelving systems and office furniture often employ punched tubing as an adjustable mounting surface for shelving, work surfaces, and other furniture components. Such punched tubing typically comprises a U-shaped channel or square box beam having a plurality of equally spaced slots along its length. Several rows of slots may be provided in a single tube. Clips on a shelf bracket or other furniture component are adapted to fit into one or more slots in the tube to support the shelf bracket or other piece of equipment. A typical application comprises a pair of vertically oriented slotted tubes, mounted to the studs in an office wall, having shelf brackets mounted thereon and extending outwardly therefrom, and a shelf supported on top of the shelf brackets. Slotted tubes are also used for many other applications in the furniture and other industries.
Generally, slotted tubes are produced by punching slots into a preformed U-shaped channel or box beam workpiece. A punch press cycles vertically up and down to force a cutting tool through the material of the workpiece, thus punching out a piece of material to form a slot of predetermined size. A mandrel supports the underside of the workpiece and has a recess sized to receive the cutter as it passes through the workpiece, aiding the cutter to make a clean cut through the workpiece material. Several slots may be cut with each cycle of the punch press, but the workpiece must generally be fed longitudinally under the punch press in a controlled series of steps so that repeated punches by the punch press produce slots along the entire length of the workpiece. The longitudinal motion of the workpiece must be accurately controlled so that successive slots are cut accurately; the required tolerance is generally only a few thousandths of an inch. Several machines and methods have been proposed to accurately align the workpiece under the cutters.
U.S. Pat. No. 4,744,276 to Duce, issued May 17, 1988 discloses one method and apparatus for punching apertures in the walls of the square sectioned steel tubes. A punching machine comprises a power punch having a punch head which is movable in a vertically up and down direction upon operation of a foot pedal. The machine supports a long square section mandrel which is sized to fit neatly into the interior of a square sectioned tube placed thereon. A laterally movable drive sleeve is mounted on the mandrel for controlling the position of the tube relative to the mandrel. The tube slides along the mandrel, yet is not securely gripped in any fashion.
In practice, the tube is pushed over the mandrel until it engages the drive sleeve and continues until the drive sleeve is in the most rearward position. The drive sleeve then pushes the tube forwardly a predetermined distance to properly position the tube under the punch head. The press is stroked by depression of the pedal so that the punch head moves downwardly, causing a punch pin on the punch head to punch out an appropriately shaped aperture. The tube is then moved forwardly along the mandrel by means of the drive sleeve until it is properly positioned to punch the next aperture.
Proper positioning of subsequent apertures is aided by means of a pin extending downwardly from the punch head a predetermined distance from the punch pin, and which fits into the previously punched aperture, thus ensuring that subsequent apertures will be punched a predetermined distance apart. Because the tube is loose on the mandrel, a slight positioning adjustment is possible by the alignment pin. The pin alignment method, however is not well suited to rapid punching.
A related problem in punch presses in general is the access to the work area. U.S. Pat. No. 4,192,209 to Urbanski, issued Mar. 11, 1980 discloses a portable reduced sized hydraulic cutter and punch assembly which is designed an adapted to cut and punch a cable tray in the field. Each cable tray comprises two opposing C-shaped channels with support members disposed at predetermined intervals between the channels. The support members prevent the channel from being moved longitudinally through the work area, requiring a means to access the work area from an alternate direction.
The Urbanski machine comprises an upper pivotable assembly rotatably mounted to a fixed lower assembly. The upper assembly comprises a cylinder. A cutoff blade and assorted punches mount to and are adapted for vertical operation by means of the cylinder. The rotational operation of the upper assembly allows an operator to insert one channel of the cable tray into the machine, stroke the cylinder to punch and cut in a single operation, rotate the upper assembly open, flip the cable tray to insert the opposing channel into the machine, rotate the upper assembly closed and punch and cut the opposing channel. The cable tray is not moved longitudinally through the work area. Rather, the pivoting upper assembly permits manual insertion of different sections of the cable tray into the machine for punching, and must be opened for each stroke of the punch press.